Break out number parsing into its own function

It's time to parse the full JSON spec for numbers.

Signed-off-by: Casey Dahlin <cdahlin@redhat.com>
Fixed point arithmetic

We use fixed-point instead of floating-point numbers for more reproducible
results.

This gives us most of the JSON syntax, but we still don't have exponentiation.

Signed-off-by: Casey Dahlin <cdahlin@redhat.com>
Rename ASON_ constants to TYPE_

Signed-off-by: Casey Dahlin <cdahlin@redhat.com>
Rename VALUE_ constants to ASON_

Signed-off-by: Casey Dahlin <cdahlin@redhat.com>